Translation of abstract (English)

In the presented thesis an extensive data set originating in the subpolar North Atlantic was compiled and analyzed. This set covers measurements of tritium, helium, neon and O-18. The main focus in the analysis was the formation and subsequent spreading of the deep water masses and its variability on time scales of several years. Investigating averaged tracer data that were calculated by use of an optimal interpolation algorithm, it became evident that the convective formation of Labrador Sea Water (LSW) and its spreading west of the Mid Atlantic Ridge (MAR) came almost to an halt in the years between 1994 to 1997, whereas the freshening of the intermediate layer east of the MAR still continues. An estimation of the spreading time between the Irminger and the Iceland Basin as well as between the Iceland Basin and the Rockall Trough yielded < 3 yrs and 1-2 yrs, respectively, well in accordance with results of other publications. The overflows DSOW and ISOW, on the other hand showed no significant temporal trend in their current speed. A multiparameter analysis in the vicinity of the Labrador and Irminger Basin showed clearly that continuous mixing between the various water masses results in an observable modification of the parameter values along their advection paths. However, despite the incorporation of mixing processes in the analysis, the parameterization of the DWBC spreading rate was very much impaired by the currently low gradient of the tritium input function and the substantial inventory of bomb tritium in the whole water column.